Barry Allen was born in a small Iowa town and grew up loving science and comic books. He got a scholarship to college and graduated in three years with a major in Organic Chemistry and a minor in Criminology. Though he was offered higher paying jobs elsewhere, he took a job as police scientist for Central City PD. Iris West, a photojournalist, settled in Central City. She met Barry at a crime scene and they became inseparable. Barry soon got the courage to propose, and she accepted.
One night while finishing up some tests, lightning struck Barry's office. That night, he realized he'd been given the powers of his comic book hero - the Flash. Barry adopted the Flash name, but created his own costume out of a material he'd invented. He kept it in a ring which could remove the hydrogen particles from it and deflate it. With superheroes and super criminals popping up all over the country, the Flash banded together with some of the other costumed heroes as the Justice League of America. He formed a tight bond with Green Lantern.
Iris' brother and his wife let their ten year old son, Wally West, stay with them when he was ten. In the year since the Flash had began, young Wally had become his biggest fan. One afternoon, Barry agreed to introduce Wally to the Flash. At his lab, the Flash was telling the boy how he'd become the Flash when lightning again struck. Wally was hit with chemicals and became supercharged, too. They made him a costume and he was dubbed Kid Flash ("Speedy" was already taken). Soon, Kid Flash got his own costume, not just a smaller version of Barry's. Eventually, Barry shared his dual identity with his nephew, and they even let Iris in on it.
As the Flash, Barry fought dozens of the costumed criminals in his city and around the world: Captain Cold, Heat Wave, Mirror Master, Trickster, the Pied Piper, Dr. Alchemy / Element Man, Weather Wizard, Gorilla Grodd, Abra Kadabra, and the most deadly - Professor Zoom, the Reverse Flash. Zoom was from the future, so he knew everything about the Flash and who his loved ones were.
Barry discovered Keystone City, the home of the original Flash. Somehow, it vibrated at a frequency different from that of the rest of the Earth, leaving it invisible, yet occupying the same Earth. Barry found Jay Garrick, and together, they destroyed the device separating the two cities and the men behind it. Jay, too old to continue as the Flash, gave Barry his blessing with the name.
With their wedding date approaching, Barry's secret identity became public knowledge. Using one of his scientific inventions, he was able to turn back the hands of time and stop it from happening. Before he went back, Iris made him promise to tell her before they were married. Barry broke his promise. Zoom attacked the wedding, but without anyone knowing it, Flash defeated him. Iris later learned (again) Barry was the Flash when she heard him talking in his sleep about the incident. Secretly, she gave him until their first anniversary to tell her. On that day, he did. He also told her they were able to have children, but they both agreed to wait for the time being.
When one of Barry's friends from the force was killed on duty, he and Iris took in his daughter, Stacy, who was in her first year of college. In another strange twist of fate, Iris learned - as she'd always suspected - she was adopted. Not in the normal sense - her parents were from the 30th century. They'd sent her back in time to avoid an Armageddon when she was just an infant.
Professor Zoom, hell-bent on destroying Barry, attempted to steal his wife. When she denied him, he killed her. Months past and Barry buried himself in work. He moved out of the house to get away from the memories and eventually found someone else - Fiona Webb. She was in witness protection and the Flash had taken down the man who would have been her killer. Barry proposed.
On their wedding day, Zoom reappeared and threatened her. The Flash went after him, leaving Fiona alone at the altar. He stopped Zoom in a headlock inches before he got to the would-be Mrs. Allen. As he checked on her, he was arrested for manslaughter - Zoom was dead. Since Barry had stood his bride up at the altar, he decided to leave that identity behind. The Flash died his hair and had his face surgically altered, as he feared he would have to unmask in court. Abra Kadabra was secretly influencing the jurors against the Flash. He was found guilty.
One of the jurors revealed himself to the Flash as his dead wife, Iris. Her birth parents had brought her back to their time a split second before Zoom had killed her. Watching from the future, Iris knew about Abra Kadabra's tampering and out maneuvered him. She brought Barry back with her to the 30th century. Weeks later, cataclysms struck. Barry once again had to be the Flash. He was whisked back in time and used his powers to destroy the devices of the Anti-Monitor, helping save the universe (see Crisis on Infinite Earths). Iris looked up his death and broke down. Only the twins growing in her womb gave her comfort.
The Tornado Twins, Don and Dawn, received their father's super speed, but were killed in combat. Don's son (Bart) encountered hypermetabolism and was taken in for experimental treatment. Iris took him back to the 20th century before he could be captured and corrupted. There, Wally - now the Flash - watched him grow and adopt the superhero name Impulse. Max Mercury, a time-travelling speedster, was entrusted with Impulse and became his guardian.